Solution to problem 14 in Python

src/Year_2018/P14.py

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+# --- Day 14: Chocolate Charts ---
+
+# You finally have a chance to look at all of the produce moving around.
+# Chocolate, cinnamon, mint, chili peppers, nutmeg, vanilla... the Elves must be
+# growing these plants to make hot chocolate! As you realize this, you hear a
+# conversation in the distance. When you go to investigate, you discover two
+# Elves in what appears to be a makeshift underground kitchen/laboratory.
+
+# The Elves are trying to come up with the ultimate hot chocolate recipe;
+# they're even maintaining a scoreboard which tracks the quality score (0-9) of
+# each recipe.
+
+# Only two recipes are on the board: the first recipe got a score of 3, the
+# second, 7. Each of the two Elves has a current recipe: the first Elf starts
+# with the first recipe, and the second Elf starts with the second recipe.
+
+# To create new recipes, the two Elves combine their current recipes. This
+# creates new recipes from the digits of the sum of the current recipes' scores.
+# With the current recipes' scores of 3 and 7, their sum is 10, and so two new
+# recipes would be created: the first with score 1 and the second with score 0.
+# If the current recipes' scores were 2 and 3, the sum, 5, would only create one
+# recipe (with a score of 5) with its single digit.
+
+# The new recipes are added to the end of the scoreboard in the order they are
+# created. So, after the first round, the scoreboard is 3, 7, 1, 0.
+
+# After all new recipes are added to the scoreboard, each Elf picks a new
+# current recipe. To do this, the Elf steps forward through the scoreboard a
+# number of recipes equal to 1 plus the score of their current recipe. So, after
+# the first round, the first Elf moves forward 1 + 3 = 4 times, while the second
+# Elf moves forward 1 + 7 = 8 times. If they run out of recipes, they loop back
+# around to the beginning. After the first round, both Elves happen to loop
+# around until they land on the same recipe that they had in the beginning; in
+# general, they will move to different recipes.
+
+# Drawing the first Elf as parentheses and the second Elf as square brackets,
+# they continue this process:
+
+# (3)[7]
+# (3)[7] 1  0
+#  3  7  1 [0](1) 0
+#  3  7  1  0 [1] 0 (1)
+# (3) 7  1  0  1  0 [1] 2
+#  3  7  1  0 (1) 0  1  2 [4]
+#  3  7  1 [0] 1  0 (1) 2  4  5
+#  3  7  1  0 [1] 0  1  2 (4) 5  1
+#  3 (7) 1  0  1  0 [1] 2  4  5  1  5
+#  3  7  1  0  1  0  1  2 [4](5) 1  5  8
+#  3 (7) 1  0  1  0  1  2  4  5  1  5  8 [9]
+#  3  7  1  0  1  0  1 [2] 4 (5) 1  5  8  9  1  6
+#  3  7  1  0  1  0  1  2  4  5 [1] 5  8  9  1 (6) 7
+#  3  7  1  0 (1) 0  1  2  4  5  1  5 [8] 9  1  6  7  7
+#  3  7 [1] 0  1  0 (1) 2  4  5  1  5  8  9  1  6  7  7  9
+#  3  7  1  0 [1] 0  1  2 (4) 5  1  5  8  9  1  6  7  7  9  2
+
+# The Elves think their skill will improve after making a few recipes (your
+# puzzle input). However, that could take ages; you can speed this up
+# considerably by identifying the scores of the ten recipes after that.
+# For example:
+
+#     If the Elves think their skill will improve after making 9 recipes, the
+# scores of the ten recipes after the first nine on the scoreboard would be
+# 5158916779 (highlighted in the last line of the diagram).
+#     After 5 recipes, the scores of the next ten would be 0124515891.
+#     After 18 recipes, the scores of the next ten would be 9251071085.
+#     After 2018 recipes, the scores of the next ten would be 5941429882.
+
+# What are the scores of the ten recipes immediately after the number of recipes
+# in your puzzle input?
+
+
+def part_1() -> None:
+    target_recipes = int(open("files/P14.txt").read())
+    recipes = [3, 7]
+    elf1, elf2 = 0, 1
+
+    while len(recipes) < target_recipes + 10:
+        recipes += list(map(int, list(str(recipes[elf1] + recipes[elf2]))))
+
+        lr = len(recipes)
+        elf1 = (elf1 + int(recipes[elf1]) + 1) % lr
+        elf2 = (elf2 + int(recipes[elf2]) + 1) % lr
+
+    scores = "".join(map(str, recipes[target_recipes : target_recipes + 10]))
+
+    print(f"The scores are {scores}")
+
+
+# --- Part Two ---
+
+# As it turns out, you got the Elves' plan backwards. They actually want to know
+# how many recipes appear on the scoreboard to the left of the first recipes
+# whose scores are the digits from your puzzle input.
+
+#     51589 first appears after 9 recipes.
+#     01245 first appears after 5 recipes.
+#     92510 first appears after 18 recipes.
+#     59414 first appears after 2018 recipes.
+
+# How many recipes appear on the scoreboard to the left of the score sequence
+# in your puzzle input?
+
+
+def part_2() -> None:
+    target_recipe = [
+        int(i)
+        for num in open("files/P14.txt").read().splitlines()
+        for i in num
+    ]
+    recipes = [3, 7]
+    elf1, elf2 = 0, 1
+
+    # The second part of this condition ensures that the recipe is found even
+    # if it is finished by the '1' in the tens column of a sum.
+    while (
+        target_recipe != recipes[-len(target_recipe) :]
+        and target_recipe != recipes[-(len(target_recipe) + 1) : -1]
+    ):
+        score = recipes[elf1] + recipes[elf2]
+
+        if score >= 10:
+            recipes.append(1)
+            recipes.append(score - 10)
+        else:
+            recipes.append(score)
+
+        lr = len(recipes)
+        elf1 = (elf1 + int(recipes[elf1]) + 1) % lr
+        elf2 = (elf2 + int(recipes[elf2]) + 1) % lr
+
+    nrecipes = (
+        len(recipes)
+        - int(recipes[-len(target_recipe) :] != target_recipe)
+        - len(target_recipe)
+    )
+    print(f"There are {nrecipes} recipes")
+
+
+if __name__ == "__main__":
+    part_1()
+    part_2()